Join the Mages Guild is a quest available in The Elder Scrolls IV: Oblivion. If the Hero would like to join the Mages Guild, they must not have any bounties on them and receive recommendations from all the guild hall leaders in the major cities.

Once all the recommendations have been received, head to the Arcane University in Imperial City and speak to Raminus Polus. He names the Hero Apprentice of the Mages' Guild and gives them the Robe of the Apprentice, which increases Willpower.